Bug fix: Enhance embeding model to give better error message (#15346)

To resolve https://github.com/infiniflow/ragflow/issues/15343 enhance
the model embedding message to give extact failure message to customer.


# QWen

## Retrieval
<img width="3321" height="1033" alt="image"
src="https://github.com/user-attachments/assets/6b82921a-a3a7-4a33-a383-1cf316398ee2"
/>

## Chat
<img width="2241" height="311" alt="image"
src="https://github.com/user-attachments/assets/ec311365-62d5-407a-8915-5c8d72be9716"
/>


# SiliconFlow
## Retrieval
<img width="3321" height="1033" alt="image"
src="https://github.com/user-attachments/assets/ee2cd191-a27d-4729-b53d-2fbdb4e352cd"
/>

## Chat
<img width="1562" height="210" alt="image"
src="https://github.com/user-attachments/assets/10376a8e-a3f4-422f-bc2e-96f2a8a96448"
/>

# Baichuan
## Retrieval
<img width="3321" height="1107" alt="image"
src="https://github.com/user-attachments/assets/dcb5409d-f7fc-4804-b186-5e1ee11e09c4"
/>

## Chat
<img width="2241" height="311" alt="image"
src="https://github.com/user-attachments/assets/ec311365-62d5-407a-8915-5c8d72be9716"
/>


# Zhipu
zhipu is good.

common/exceptions.py

@@ -26,3 +26,9 @@ class ArgumentException(Exception):
 class NotFoundException(Exception):
     def __init__(self, msg):
         self.msg = msg
+
+class ModelException(Exception):
+    def __init__(self, msg, retryable=False):
+        super().__init__(msg)
+        self.msg = msg
+        self.retryable = retryable